1S99] E WART'S PENYCUIK EXPERIMENTS 209 



Believing that the inbreeding of race-horses in Britain has now 

 passed beyond the limit of stability, and that the stock is on the down- 

 grade, — a danger dreaded by many with an anxiety which seems to 

 others uncalled for — Professor Ewart points out that the racer, whose 

 artificial evolution has cost so much, may be saved by bringing in fresh 

 blood in the form of imported Barb and Arab mares (as Sir Everett 

 Millais saved his Bassets by bringing in bloodhounds), or by crossing 

 with imports from America and Australia, which have become somewhat 

 different in their new environment. 



All this is of much interest in connection with mankind. Thus it 

 has been maintained, as recently by lieibmayr (Nat. Sci. xiv. p. 95), 

 that the evolution of a human race implies alternating periods of 

 dominant inbreeding and dominant cross-breeding. The inbreeding 

 is necessary to give fixity to character, the cross-breeding is necessary 

 to avert degeneracy and to stimulate new variations which form the 

 raw material of future progress. The antithesis between the Jews 

 with their persistent inbreeding, and the complex cross-breeding at 

 present conspicuous in America, is one of almost diagrammatic vividness. 



On the vexed question of the sterility of hybrids and what it 

 means when it occurs, Professor Ewart has not as yet been able to shed 

 much light. It is well known that hybrids between different species 

 are sometimes cpiite fertile, as in the case of the crosses between 

 common goose and Chinese goose, common duck and pintail duck ; in 

 other cases, however, the result is sterility. Thus it has not been proved 

 that a female mule has ever produced a foal, though she may produce 

 milk. It is remarkable that the reproductive organs do not seem to 

 have been investigated either in mule or hinny. 



In the two-year-old zebra-horse hybrid liomulus, the reproductive 

 organs and instincts seem to be fully developed, but the reproductive 

 elements are still immature (with the merest rudiment of a tail). The 

 same was true of a male zebra-ass hybrid, which unfortunately died. 

 In a female zebra-mule (zebrule), the reproductive organs, which were 

 of a zebroid type, seemed normal, and the ovary showed well-developed 

 follicles ; but no proof of fertility has yet been obtained in any case. 

 A nine-year-old zebrinny (horse-zebra hybrid) seemed sterile with both 

 Arab and Clydesdale horses. 



Telegony. 



The interest which is so often aroused by obscure phenomena is 

 well illustrated in connection with telegony, — or the supposed influence 

 of a sire on offspring not his own, but by the same mother. The 

 literature of the subject suggests that dealing with the somewhat 

 cognate problem of maternal impressions, it tends to be anecdotal 

 rather than precise. The discussion practically dates from Lord 

 Morton's famous letter to the Koyal Society (1820), in which he related 



15 NAT. SC— VOL. XIV. NO. 85. 



